ABB Alamo Dry (Oil-less) bushings Tutorial

© ABB Group May 18, 2015 | Slide 1

ABB AlamoDry (Oil-less) bushingsTutorial

MEA – Springfield, IL – May 2015

David M. Geibel, Tecnical Director

Introduction - Transformer

Big Gray

Box

Spark Plugs

We have been “bushings” for a long time


ABB Alamo: World Leader - OIP Condenser Bushings

Standards: IEEE and CSA

25 kV through 550 kV

400 A through 21,500 A

Bushings!

IS

WHO

WE

ARE!!!


Why Dry? Why Silicon? Why RIS?

No oil to leak

No oil to contaminate

No oil to burn

No pressure vessel to rupture

High seismic performance

Long life

Easy Storage

100,000+ dry bushings produced

Dry Bushings

Advantages

Reduced risk of fire

Oil leakage is eliminated

Mechanically rigid design and no need for

oil supervision

Seals the transformer and reduces

the down-time in the event of major

TFO failures

Lightweight and compact, less than 50% of

OIP

Transported, stored and installed at

any angle

Can be energized immediately

after installation

Important

Needs to be stored properly long-term

Dry Bushings intentional fault testing (63kA X 0.5Sec)

Voltage Distribution

75%

50%

25%

25%50%

75%

Uncontrolled field follows the laws of nature unequally

stressing porcelain, oil, epoxy and/or paper insulation

system

Field controlled by capacitive

grading follows controlled

contours making effective use of

all insulation

No Capacitive

Grading (bulk

bushing)

Capacitive

Grading (condenser

bushing)

Function of High Voltage Bushing

Capacity-controlled

electrical field

Uncontrolled

(natural) electrical field

0%

voltage

100%

voltage

Electric Field Distribution in and around Bushings

Grounded

flange

Oil Impregnated Paper (OIP)

15 kV to 800 kV

Plain paper condenser body

Core impregnated with hot oil under vacuum

Aluminum foil or ink print gradients

Partial discharge 10 pc at 1.5 times line to ground

Power factor requirements – less than .50%

Resin Bonded Paper (RBP)

Cast Epoxy

Resin Impregnated Paper (RIP)

Resin Impregnated Synthetic (RIS)

Condenser Core Types



15 kV to 230 kV

Resin treated plain paper condenser body

Dry processed with varnish dipped core

Aluminum foil gradients


Power factor requirements – less than 2.0%

Cast Epoxy







Westinghouse type S and OS

Cast Epoxy


Resin Impregnated Synthetic

(RIS)



Cast Epoxy

15 kV – 138 kV

Metal screen mesh graded

Epoxy resin condenser body


Power factor requirements – less than 1.0%






Cast Epoxy


15 kV to 800 kV

Crepe paper condenser body

Resin impregnated core under vacuum


Partial discharge free although guideline of 10 pc








Cast Epoxy



25 kV to 161 kV

Synthetic mesh condenser body

Encapsulated with resin under vacuum


Partial discharge free although guideline of 10 pc





Cast Epoxy



Molded design condenser body


RIP vs. OIP technology

RIP Technology

tube / conductor

main insulation

RIP body with

fine gradingdry filling

Micagel

porcelain or

composite insulator test tap

flangeair side

oil side

R esin

I mpregnated

P aper

RIP Technology

Tube / conductor

Main insulation

RIP body with

fine grading

Dry filling

Micagel

Porcelain or

composite

insulator

Flange

Modern Bushings Production

3D-ConstructionDielectric

Mechanics

Thermic

Modern RIP Bushings Production

Conductor:

- Al, Cu,

- solid, tube

Special

crepe paper

Aluminium

foils

Modern Bushings Production

Winding-Process

Paper -Drying

Resin-Impregnating

Curing Process

RIP Bushings Technical Facts

Low dielectric losses (Power Factor < 0,4%)

PD “free“up to double service voltage

Excellent mechanical strength

Excellent Siemic withstand capablity

Fire resistant (oil free)

High thermal strength (class E, 120°C )

No oil to leak out, contaminate, degrade

High design flexiblity for custom mechanical fit

SeismicRIP® Bushings

SeismicRIP® Bushings

New line of SeismicRIP® Oil/Air Bushings

Satisfing the highest requests as perIEEE Standard 693

Nominal voltages from 69 up to 550kV

RIP technology with composite insulator

Delivered to Californian utilities

Transformer BushingsOil – Air application

High Voltage Bushings

24-550 kV

up to 5,000 A

with

porcelain or

silicone composite insulator

SeismicRIP ® Bushings

69-550 kV

up to 5,000 A

only with silicone composite insulator

Transformer BushingsOil – Oil bushings

for cable box

72.5 – 550 kV

up to 4000 A

with double flange available

Transformer BushingsOil – SF 6 application

For GIS connection

72.5 – 550 kV

Up to 4000 A

GSU Transformer BushingsOil – Air high current

17,5 – 52 kV

Up to 40kA

With

Porcelain

Silicone composite

insulators

Three Gorges Project – China

Micafil supplied:

SF6/Air bushings550 kV, 4000 A

Transformer high current bushings24 kV, 35,000 A


ABB Alamo: O Plus Dry™

Standards: IEEE

2015


400 A through 1,200 A

By late 2015


2000 & 3000 Ampere

Coming soon:

230kV (800 – 5,000 Amp)

69kV

400/1200A

Same condenser theory

1 2

4 56

1

2

4

5

3

6

2 4 53 61

V/6

V/6

V/6

V/6

V/6

V/6

V

2 4 5 631

6/6 V

5/6 V

4/6 V

3/6 V

2/6 V

1/6 V

Effect of Capacitive Grading

Capacitive Layer

3

CL

EasyDry Bushing Construction Synthetic mesh fabric

Used in winding

condenser

Provides structure &

supports foils that form

condenser

Open structure allows

easy impregnation

Synthetic material

does not absorb

moisture

EasyDry Bushing Construction Isolation of conductor

EasyDry Bushing Construction Synthetic mesh fabric winding

EasyDry Bushing Construction Foil “Equalizers”


New CondenserType O Plus Dry™

Windings

Conductor

Isolator

Synthetic Mesh

Equalizer Foils

Tap connections

Condenser

Winding

Filled Epoxy

No Machining

Condenser

Winding

EasyDry Bushing Construction Critical Resin Curing

EasyDry Bushing Construction Epoxy “factory”


New CondenserType O Plus Dry™

Windings

Conductor

Isolator

Synthetic Mesh

Equalizer Foils

Tap connections

Condenser

Winding

Filled Epoxy

No Machining

Condenser

Winding

EasyDry Bushing Construction Flange Installation

EasyDry Bushing Construction Condenser Preparation


New Manufacturing PracticesType O Plus Dry™ Weather shed extruder

World class silicon

High Temperature Vulcanized

Modern shed profile

Infinitely variable

Reduced lead time


New Weather Sheds Type O Plus DryTM

HTV Silicon

Extruded

Helical

Directly

Applied


New Weather Sheds Type O Plus DryTM

“Homogeneous”

turn-to-turn joint

(Undetectable

joint)

EasyDry Bushing Construction Final Assembly

Resin Impregnated Synthetic

Circuit

BreakersCable

Terminations

Instrument

Transformers

Bushings Surge

Arresters

Composite Insulator Aplication through 1200kV AC/DC

Just ABB Service experience

World wide in > 60 countries and >80 000 composite

insulators

Glass fiber reinforced

epoxy resin tube

Silicone rubber sheds

Aluminum end fitting

Composite insulatorsOne-piece design

Glass fiber reinforced epoxy resin tube using wet filament winding technique

Tailored mechanical and electrical performance

Continuous one-piece tube design for length >15 m (no gluing of tube segments)

Conical and cylindrical design available in length >15 m

Glass fiber composite tubeOne-piece design

Silicone Insulators

Reduced maintenance

Hydrophobic surface

Reduced leakage currents

Longer cleaning intervals

compared to porcelain

Improved safety

Non shattering

Non flammable

Increased seismic withstand

Self extinguishing when exposed

to open fire

Hydrophobicity

Silicone is by nature more

hydrophobic than porcelain or

other polymers

Constant diffusion of silicones to

the surface

Water on a hydrophobic surface

stays as water droplets and does

not form a continuous film

Automatic hydrophobicity recovery

after possible temporary reduction

under constant heavy pollution

No ageing effect on hydrophobicity

Gives excellent pollution

performance with minimum

maintenance

Maintenance of HTV shed bushings

Self-Cleaning(Hydrophobic = self cleaning)

Degrees of hydrophobic performance

Good Bad

Advantages with Silicone Rubber Sheds

Flashover resistant

Insulator surface hydrophobic

Water stays as droplets

The leakage currents are suppressed

Tracking resistant

Ageing withstand

Less discharge activity in case of severe

pollution

UV stability

Max. absorption below wavelength

of natural UV-light

Mechanical strength

Elastic and stable over a wide

temperature range

Composite insulatorsManufacturing processes

One continuous seamless outer silicone housing for length >15 m

Manufacturing in one step without parting lines/ mold lines or joints

Flexible production method for different diameters, lengths, shapes and creepage distances

Silicone rubber housing Seamless helical extrusion process

Shed tip with large radius and “drip edge” to minimize the electrical field and the risk of flashover

Inclined bottom surface gives high protective creepagedistance and lowest possible leakage currents

Special shed profile fulfilling requirements for 800 kV UHVDC

Silicone rubber housing Optimized shed profiles

Injection molding Helical extrusion

High protective creepage distanceLow protective creepage distance


Injection

moldingHelical

extrusion

No mold linesMold lines

Low electrical fieldHigh electrical field

Shed profile ≠ Shed profile


ExperienceWell verified design

Quality and -50°C performance approved by Hydro Quebec

Pressure cycling test ANSI C37.09

10 000 cycles 0 to MSP at -40°C

90 000 cycles 0 to MSP at +100°C

Performed on several insulators, including the most severely loaded tube and joint in pressure

Tube surge arresters qualified for -60°C IEC60099-4

Performed on the most severely loaded joint in bending

Long term performance verified in field and test stations

Dungeness, UK

Guangzhou, CN

Ludvika (800 kV DC), SE

Koeberg (KIPTS), ZA

Silicone rubber materialHTV for reliable performance

Silicone rubber usually discussed in 3

general classes

RTV - Room temperature

vulcanizing

LSR - Liquid silicone rubber

HTV - High temperature vulcanizing

ABB HTV Insulator after 1 year KIPTS test

Lower quality Insulator after 1 year KIPTS test

Silicone Rubber ≠ Silicone

Rubber

Koeberg Insulator Pollution Test Station (KIPTS)ESKOM, ZA

Severe test station for pollution and ageing performance of insulators

Very harsh environment for insulators:

Salt fog

Strong UV light

Sand

Industrial pollution

Pollution level up to 6 times “very heavy” from IEC 60815

12 month test cycle

Severe service experience Long term test at KIPTS

Composite

Insulators tested

successfully at

Koeberg Insulator

Pollution Test

Station (KIPTS)

High-temperature vulcanized (HTV) silicone from well known sub-suppliers

Highest durability of sheds

Superior performance in sandstorm areas

Minimization of damages during transportation and handling

High amount of Aluminum Trihydrate(ATH)

Improved tracking and erosion performance

Increased fire resistance capability

Outstanding long term performance

Silicone rubber materialHigh-temperature vulcanized (HTV) silicone

Bushing after 4 years at coastal testing station

(IEC pollution level IV - Very Heavy)

Severe service experience Long term test at Dungeress, UK

ABB Composite Insulator Training

Handling, cleaning, repair

Handling

Put slings around flanges, never on silicone

Be careful with sealing surfaces and silicone

Protect sheds during assembly, construction and

maintenance

Picture courtesy of CIGRE WG3.21

Maintenance of HTV shed bushings

Cleaning

Hydrophobic and self cleaning

The right Alcohol!!

Denatured Alcohol is poisoned ethanol (poisoned with

what???)

Methanol is not recommended

Use Isopropyl Alcohol contaminated/diluted only with

water.

Water with or without mild detergent is ok if rinsed.

Repair?

On site repairable damage types

Type A. Cut or crack at shed tip

Type B. Closed cut or crack

in shed

Type C. Piece of shed is

broken

ABB Composite Insulator Training

Summary

Explosion proofMaximum safety of personnel and equipment

Non-brittleReduced handling damage risk

Excellent insulationPossible to reduce the creepage distance with at least one pollution level

Low weightEasier handling and reduced foundation loads

Maintenance freeNo cleaning in polluted environments

Outstanding seismic performanceFor best safety and reliability

Explosion proof

Non-brittle

Excellent insulationLow weight

Maintenance freeSeismic performance

Composite Insulators for HV equipment Value for the Customer

One piece tailored glass fiber composite tubeBest mechanical performance

High Temperature Vulcanized (HTV) silicone rubber with high amount of ATH fillerImproved tracking and erosion performance and best long term performance

Seamless helical extrusion process for a continuous outer silicone housingNo mold lines where dirt/ salt can accumulate or joints/ weak spots

Optimized shed profiles with large shed tip radius and high protective creepage distance Lowest possible leakage currents and electrical field

Experience since 1985 and > 80 000 insulators

installed in all climatesReliable long term performance

Composite Insulator TechnologyDesign for reliable performance


Applying Mature Weather Shed TechnologyType O Plus DryTM





Recent Cigre paper concludes life of HTV

weather sheds good for life of bushing

(copies available).

This field study indicates “in service”

insulators in good condition under various

conditions.

Holding up well even in the most severe

environments.

1100 kV Oil-less wall bushings

600 kV DC Dry bushing.



No mold linesMold lines

Low electrical fieldHigh electrical field

Shed profile ≠ Shed profile

Injection

moldingHelical

extrusion

Short term storage of RIP/RIS bushings

Short term = less than one year

Store indoors in the original packaging materials

• Store where wildlife cannot

damage silicon sheds (rats,

birds etc.)

Longer term storage of RIP/RIS bushings

RIP condensers contain paper and are

machined to finished shape exposing paper

Store indoors away from direct sunlight

Store with silicon sheds not supporting

weight of bushing

Where wildlife cannot damage silicon

sheds (rats, birds etc.)

Must be stored in moisture tight bag or

metal tank over lower end and protected

from all moisture

Longer term storage of RIP/RIS bushings

RIS condensers contain no paper and are not

machined to finished shape

Store indoors away from direct sunlight

Store with silicon sheds not supporting weight of

bushing

Store where wildlife cannot damage silicon

sheds (rats, birds etc.)

Currently recommending moisture tight bag over

lower end

Permanent storage options

Permanent storage options

Wide range of applications

RIP applicable to bus duct installations

Development testing more intense

PD levels

Essentially none

Thermal testing

Specific to materials

Mechanical testing

To Fracture

CAT scans (void detection)

Dielectric testing

Extensive

Long term withstand

Proof of Altitude

New Routine testingType O Plus Dry™

Partial discharge:

Essentially background level of

facility (<5 pc) at 2xLG

Withstand extended (5 min.)

Leak tests:

No oil to leak from bushing

Test must ensure xfmr oil cannot

pass through bushing

Helium testing vac&press

Molded condenser verification:

Glass transition temp

Close SPC and chemical

verification

OIP has loss of life as insulation polymer chains

disintegrate, but this is function of time and temperature.

Dry bushings made with polymers, such as epoxy, are

much more sensitive to temperature for short times (like the

gaskets in OIP).

When the epoxy reaches glass transition temperature (Tg),

it begins to quickly turn into something(?) new and

dielectric performance is lost. No oil to fill voids. Damage

is irreversible.

Dry bushing Overload?


Thermal design of RIP/RIS oil-less bushings

Glass transition vs thermal rating

Tg?

The users does

not know the

thermal margin of

each design.

Thermal Conclusions.

Plan your overload need when you spec your bushings.

Remember that bushings rating rarely are at ratings of

transformer.

Relatively short excursions may compromise the

reliability of a bushing with no obvious evidence.

Be certain about bus/terminal temperatures &

connections

Dry bushing Overload?

Power Factor and Capacitance is still your best indicator

Capacitance increase indicates shorted layer

5% increase investigate and trend

10% remove from service

Power Factor increase indicates losses increase in

insulation

Thermal damage

Partial discharge in voids

50% investigate and trend

100% increase remove from service

Field assessment of RIP/RIS oil-less bushings

Power Factor and Capacitance is still your best indicator

Test before installation to match Name Plate

Test after installation to establish baseline

Test at 15 years in service

Test each five years thereafter

Test after long term storage

Thermal scan annually and after first loading

Visual inspection annually


Monitoring devices are available

Power Factor

Capacitance

Partial Discharge

Lab testing can be performed if suspect:

AC

Withstand at 85% of original withstand with PD

Extended 1.5 X L-G with PD

Impulse

Lightning (1.5 X 50μs)

Switching surge at 85% original levels


Technical limits of Dry

RIP lower ends absorb moisture

Hard limit for temperature

Order to Overload requirements

Vulnerable to rough handling

Your ABB Guardian Angel (or Transformer Troll?)

Michelin Man??


ABB Alamo Dry (Oil-less) bushings Tutorial

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